The present invention relates to an apparatus for the adjustment of the stroke or lift of a valve actuated by a camshaft.
Apparatus for the adjustment of the stroke of charge changing valves of internal combustion engines offer great advantages for numerous applications. For example, by reducing the stroke in the partial throttle range the mixture preparation can be improved, thereby reducing consumption and the content of noxious material in the exhaust gas.
An apparatus of this type is know from U.S. Pat. No. 4,203,397. With this apparatus, the entire U-shaped outer lever is supported on a hydraulic play-compensating element. The inner lever is mounted at the free end of the arms of the outer lever. A blocking device for blocking the pivotability of the inner lever relative to the outer lever is provided with a pivot element that is mounted on the arms of the outer lever adjacent to the free end region of the inner lever; by means of a stationary electro magnet, the pivot element is pivotable into the path of movement of the inner lever, thereby blocking the pivotability of the inner lever relative to the outer lever. The camshaft has a full stroke cam that cooperates with a contact surface of the inner lever, and partial stroke cams that are disposed on both sides of the full stroke cam and cooperate with contact surfaces of the outer lever. The construction of the blocking mechanism is relatively complicated. Furthermore, the outer lever is a relatively complicated, space-consuming and heavy component due to its support upon the valve play-compensating element and the mounting not only of the inner lever but also of the blocking element on the outer lever.
U.S. Pat. No. 5,544,626 discloses a valve disengagement device that has a two-part valve lever, whereby an outer lever has an overall U-shaped configuration and is supported via its crosspiece on a hydraulic valve play-compensating element. Mounted on the ends of the arms of the U is an inner lever that carries a roller for contacting a cam of the camshaft. The free end of the inner lever can be interlocked on the crosspiece of the outer lever in that a pin, which is movably guided in the crosspiece of the outer lever, is moved into a recess formed on the inner lever by means of hydraulic fluid pressure that acts from the hydraulic valve play-compensating element. When the blocking device is arrested, the valve lever acts like a one-part lever that transfers the cam stroke to the valve. When the blocking device is released, the inner lever extends into the outer lever, so that the valve is not actuated.
U.S. Pat. No. 5,655,488 describes an apparatus for the adjustment of the stroke of a valve, which is actuated by a camshaft, via an inner lever that is mounted within an outer lever in the region of the support of the outer lever against a component that is secured to the engine. By means of a blocking device, which displaces a blocking component disposed on that end of the outer lever that is on the valve side, the pivotability of the inner lever relative to the outer lever can be blocked.
It is an object of the present invention to provide an apparatus for the adjustment of the stroke of a valve that is actuated by a camshaft, wherein the apparatus has a straightforward construction and requires little installation space.